Symptom: 95 Korean production capacity of sodium tower sedan, equipped with KM175 series gearbox. This car has been over 300,000 km mileage, the engine has been overhauled, automatic transmission because the oil pan bumps have been overhauled. Recently due to hang R block, the big throttle to be able to take the car. Once again the automatic transmission disassembly overhaul, replace the wear clutch plate, to confirm the torque converter is also damaged. Replace a refurbished torque converter, everything is normal after loading and unloading. But after 3 months after the driving situation, the inspection, the diagnosis of automatic transmission failure, automatic transmission output power is not enough.
    Troubleshooting: the automatic transmission carried down and found that the engine crankshaft flywheel connected to the torque converter of a similar shape of the triangle of the flexible plate, in the fixed screw hole (a total of 3) all broken, torque converter off, unable to fly Synchronous rotation. Power is cut off, the gearbox power naturally can not be output. Replace a flexible board, re-installed on the train. Vehicles normal driving more than 1 month later, and on the highway "lying nest" the.
    The car back to the repair shop, carrying the gearbox inspection and found that the replacement of the new flexible plate in the screw hole fixed all broken! Carefully check, but also did not damage the automatic transmission pump and other components. Why one after another are flexible plate damage fracture, resulting in failure of the torque converter it?
    After careful inspection of the torque converter, it was found that the journal of the rear end of the flywheel crankshaft had abnormal wear marks. Measure the front end shaft diameter of the torque converter with the vernier caliper and find that its ellipticity is close to 0.12mm. Because of its bushing (the front end of the torque converter is matched with the front end of the crankshaft), the inner diameter of the bushing is also measured, Roundness up to 0.35mm. In addition, the engine flywheel housing and gearbox housing connection screw hole should have two diameter 12mm positioning pin (diagonal cross), then found only one, suspected to be caused by these two factors. So, take the following measures:
    1, re-processing a standard screw hole positioning pin sets; 2, the torque converter head journal (towards the engine) re-grinding finishing; 3, re-processing a copper crankshaft rear bushing, the hole and 4, replace a new flexible board; 5, install the gearbox, the fastening flywheel screw cross the uniform force, the test came back by the person after the re-fastening an examination.
    All in accordance with the technical requirements of the assembly, this car driving nearly 3 months after all normal, troubleshooting.
    Failure analysis: This warned us that for the automatic transmission (especially old) assembly debugging, can not only pay attention to its electronic control system, hydraulic components, force and other internal quality maintenance. The dimensions, accuracy, clearance and other conventional mechanical inspection methods of external connections are not to be missed, which is the most important prerequisite for the maintenance of automatic transmission quality. Maintenance of automatic transmission external routine has the following five points:
    1, the torque converter depends on whether the shape of the outer deformation is obvious, the appearance of the color of the shell is blue discoloration, balance iron is off;
    2, connecting the flexible plate end round beating should be greater than 0.20mm;
    3, direct drive torque converter drive hub radial round beating greater than 0.30mm;
    4, indirect drive of the gearbox input shaft radial round beating greater than 0.30mm;
    5, gear pump tooth side clearance use limit of 0.30mm.